Method of and apparatus for forming plastic



Jan. 9, 1951 LYON 2,537,311

METHOD OF AND APPARATUS FOR FORMING PLASTIC Original Filed Dec. 22, 1945F q. f.

[27 ,VE' 2'7 ZZZ. 620,905 ,4; szer Zmv Z/Xw Hiya Patented Jan. 9, 1951METHOD OF AND APPARATUS FOR FORMING PLASTIC George Albert Lyon, Detroit,Mich.

Original application December 22, 1945, Serial N 0. 636,875. Divided andthis application October 2, 1947, Serial No. 777,381. In Canada June 24,1

5 "Claims.

This invention relates to the forming of plastic and more particularlyto the forming of flat plastic articles such as sheet and the like.

This invention has been divided from my copending application, U. S.Serial No. 636,- 875, filed December 22, 1945, now Patent No.

An object of this invention is to provide a n improved method of andapparatus for forming plastic articles, such as sheet, from a plasticmix.

Another object of this'invention relates to the provision of a new wayof forming plastic from plastic mix by the use of endless belts havingpolished surfaces.

Yet another object of this invention relates to the provision of a newmethod of and apparatus for forming continuous sheets of plastic in asimple and economical manner.

In accordance with the general features of this invention, there isprovided a plurality'of cooperable belts having highly polishedsurfaces, a pressure means for forcing them into cooperation and meansfor delivering plastic-mixbetween the belts prior to their being pressedtogether whereby the mix may be formed into continuous plastic sheets. H

ln 'a'ccordance with other features of this invention there is providednovel plastic forming apparatus embracing cooperable belts pressedtogether with plastic therebetween so as to be wound on a common drum ormandrel in multiple layers and on which drum the plastic'may be latercooled.

Other objects and features of this invention will more fully appear fromthe following detailed description taken in connection with theaccompanying drawings which illustrate a single embodiment thereof andin which Figure 1 is a diagrammatic view illustrating an apparatusembracing the features of this invention and capable of practicing mynovel method.

As shown on the drawings:

The reference characters 20 and 2| designate cooperable metal sheetbelts of any suitable width and length depending upon the dimensions ofthe sheet desired.

,These belts 20 and 2| may be made of any suitable material, preferablymetal, and excellent results may be obtained by making them of stainlesssteel strip having at least one highly polished surface. Each of thebelts is adapted to be pulled from a supply drum; the belt 20 beingdrawn from a supply drum 22 and the belt 2| being drawn from a supplydrum 23. I employ a cylindrical positively driven drum 24 for pullingboth of the belts 2|] and 2| from their respective supply drums 22 and23.

The two belts 20 and 2| are adapted to be wound together in layerfashion upon the driven drum 24, which may be suitably heated. Anysuitable heating medium supplied, as for example, through a pipe 25, maybe employed for this purpose. It will, of course, be appreciated, as iswell known in the rotating drum art that the heating connection 25, aswell as the heatingconnection M in Figure 1, should be so arranged as tonot interfere with the rotation of the drum. The swivel fittings orjoints may be employed for this purpose in a manner well known to thosefamiliar with this art.

In order to press the divergent belts 2|l2| together, there is provideda pair of pressure rollers or drums 26-21, which may be likewisesuitably heated. These cooperating pressure rollers or drums 26-21 maybe suitably driven and are adapted to press together the two belts 20and 2| as they converge at the pressing area. It is, of course, clearthat the two belts 2E!-2| by reason of their angular relationship,define a space at 28 into which plastic 30 may be introduced between thepolished surfaces of the two belts 2lI--2l. Any suitable means may beemployed to introduce hot or flowable plastic between the belts, as, forexample, an extruder 29.

The plastic thus delivered between the belts at the pressure area isflattened into smooth sheet-like form; such flattened plastic taking thesmooth finish of the cooperating finished surfaces of the two belts. Thebelts in leaving the pressure roller are, together with the flattenedplastic, wound up on the drum 24. It will be noted that the beltscontact the periphery .of the drum 24 at an angle so that a space 3| isprovided at the junction of the plies of the belt and plastic and thewound-up portions of the belts on the drum.

In this space I propose to insert an additional mass of plastic 32. Thismay be effected by an extruder or the like 33. Thus, at the same time asthe belts and the intermediate sheet of plastic are being wound up onthe drum 25, an additional sheet of plastic may be introduced betweenthe mass and wound-up on the drum. If this additional extruder 33 isemployed, it is, of course, necessary that both sides of the belt v behighly finished so that a smooth finish will be belts as the belts arebeing separated in their I withdrawal from the drum. In withdrawin themfrom the drum 2 1, the belts -2c and .21 may be rewound in any suitableway on supply drums ready for reuse in subsequent plastic formingoperations.

It is believed that my novel method of forming plastic will be fullyunderstood from the aforesaid description of an apparatus for practicingthe method.

It is understood that my process is particularly adapted for the formingof synthetic thermoplastic material, such, for example, as ethylcellulose or a vinyl resin of which there are many different compoundsnow on the market.

Also if it is so desired, depending upon the type of plastic beingtreated, a lubricating fluid of the type used in the plastic industrymay be used on the polished surfaces of the belts to facilitatesubsequent stripping of the flattened plastic therefrom.

I claim as my invention:

1. In a method of forming plastic .sheeting the steps of extrudingplastic material between a pair of forming belts, pressing said beltstogether, winding said belts about a heated drum, and extrudingadditional plastic material into the juncture space at convergence ofthe belts with said heated drum. e 2. In a plastic forming machine,cooperable belts having highly polished surfaces engageable with eachother, spaced supply drums from which said belts are separately pulled,a common heated driven drum about which converging portions-of saidbelts are wound as they are pulled from the supply drums, pressure meansbetween said supply drums and the driven drum for pressing the beltstogether, means for delivering plastic material between the belts beforethe belts are pressed together, whereby the plastic is flattened intocontinuous sheet form as it is wound up about the driven drum, andplastic supply means for delivering plastic between the plies wound upon the driven drum whereby a second layer of plastic may be flattenedaround and between the layers of belts Wound up on said driven drum.

3. In a plastic forming machine cooperable belts, a pair of spacedsupply drums from each of which a belt is withdrawn towards the otherbelt, a common drum for withdrawing in a common direction said beltsfrom said supply drums and about which common drum the belts are wound,said common drum being positively 4 driven, pressure means forconverging and pressing the belts together in advance of their beingwound upon the common drum, said converging belts in advance of saidpressure means defining aplastic supply area in which plastic may beintroduced for pressing into sheet form between said pressure means andfor winding up on the common drum along with the belt, means fordelivering extruded plastic between said pressure means in advance ofthe same, and additional extruding means for delivering plastic betweenthe common drum and the plies of belts being wound up thereon.

' 4. A method of making thermoplastic sheet whichcomprises the steps ofmoving metal forming belts into convergence, heating said belts,introducing thermoplastic material into the convergence of the belts,Winding the belts with the thermoplastic material therebetween about aheated drum, completing the winding of the belts with thermoplasticmaterial therebetween about said drum, cooling the drum and the beltswith the thermoplastic material therebetween to set the thermoplasticmaterial, and unwinding the belts from the drum and stripping the setthermoplastic sheet from between the belts.

5. In a method of forming plastic sheet from thermoplastic material, thesteps -.of unwinding separate metallic forming belts from supply rolls,bringing the belts into convergence, heating the belts Where theyconverge, introducing thermoplastic material between the convergingbelts, winding the heated .belts with the thermoplastic materialtherebetween about a heated drum, at the convergence of the belts withthermoplastic material therebetween with the heated drum introducing asecond layer of thermoplastic material, completing the winding of thebelts .and thermoplastic material about the heated drum, cool-ing thedrum and the belts and the thermoplastic material therebetween, andunwinding the belts from the drum and stripping the set thermoplasticsheet therefrom.

GEORGE ALBERT LYON.

REFERENCES CITED "The following references are of record in the file ofthis patent:

